Methods of predicting the post-operative position of an IOL and uses of such methods

Abstract

The invention relates to the field of ophthalmic systems and procedures. In particular, the invention relates to the determination of the post-operative position of an intraocular lens (termed “IOL”) in an eye of a patient undergoing lens replacement surgery, which involves determining the position of the existing crystalline lens in the pre-operative eye of the patient and using that information and a single numerical constant to predict the post-operative intraocular lens position. Related methods, and computer programs for performing the methods of the invention, are also disclosed.

The invention claimed is: 
     
       1. A computerized method for selecting a replacement intraocular lens required to provide a desired optical property in a post-operative eye of a patient, the method comprising the steps of:
 (a) predicting the post-operative position of a replacement intraocular lens in the eye of the patient by:
 (i) measuring the position of the existing crystalline lens in the pre-operative eye of the patient comprising measuring the Anterior Chamber Depth of the pre-operative eye of the patient; 
 (ii) measuring the thickness of the crystalline lens in the pre-operative eye of the patient; and 
 (iii) calculating the post-operative position of the intraocular lens relative to the position of the crystalline lens in the pre-operative eye of the patient, as a proportion of the thickness of the crystalline lens in the pre-operative eye of the patient, wherein the proportion is defined by a single numerical constant (C) which is determined by the intraocular lens type; 
 
 (b) calculating by computer the optical properties of the post-operative eye of the patient in which an intraocular lens of known power and geometry is positioned as predicted in step (a); and 
 (c) prescribing an intraocular lens having a power and geometry required to provide the desired optical property in the post-operative eye of the patient. 
 
     
     
       2. The method according to  claim 1  wherein step (i) comprises measuring the axial position of the crystalline lens in the pre-operative eye of the patient. 
     
     
       3. The method according to  claim 1  wherein the numerical constant (C) is further determined by the patient type. 
     
     
       4. The method according to  claim 1  wherein the numerical constant (C) is further determined by the approach used to implant the intraocular lens in the eye. 
     
     
       5. The method according to  claim 1  wherein the numerical constant (C) defines the relationship between the post-operative position of the intraocular lens in the eye of one or more eye-operated individuals, relative to the position and thickness of the crystalline lens in the pre-operative eye of the one or more eye-operated individuals. 
     
     
       6. The method according to  claim 1  wherein the numerical constant (C) is calculated using data obtained from the two or more eye-operated individual to whom that intraocular lens type has been implanted into the eye using that implantation approach. 
     
     
       7. The method according to  claim 1  wherein the numerical constant (C) defines a fraction of the thickness of the crystalline lens in the pre-operative eye of the two or more eye-operated individuals. 
     
     
       8. The method according to  claim 1  wherein the intraocular lens type is adapted for implantation into the capsular bag in the eye. 
     
     
       9. The method according to  claim 1  wherein the implantation approach is implantation of the intraocular lens into the capsular bag in the eye. 
     
     
       10. The method according to  claim 1  wherein the numerical constant (C) is calculated from data obtained from the two or more eye-operated individuals using the following formula:
     C =(IOL measured −ACD pre )/ LT  
 
 
       wherein:
 IOL measured  is the measured position of the intraocular lens in the eye-operated individual after surgery; 
 ACD pre  is the position of the crystalline lens in the eye of the eye-operated individual before surgery; and 
 LT is the thickness of the crystalline lens in the eye of the eye-operated individual before surgery. 
 
     
     
       11. The method according to  claim 10  wherein IOL measured  is determined by measuring the Anterior Chamber Depth in the eye of the eye-operated individual after surgery. 
     
     
       12. The method according to  claim 10  wherein ACD pre  is determined by measuring the Anterior Chamber Depth in the eye of the eye-operated individual before surgery. 
     
     
       13. The method according to  claim 10  wherein the numerical constant (C) is an average value obtained from the two or more eye-operated individuals. 
     
     
       14. The method according to  claim 1  wherein the numerical constant (C) is between about 0.0 and about 1.0. 
     
     
       15. The method according to  claim 1  wherein the numerical constant (C) is about 0.4. 
     
     
       16. The method according to  claim 1  wherein measuring the Anterior Chamber Depth of the pre-operative eye of the patient comprises performing an ultrasound technique. 
     
     
       17. The method according to  claim 1  wherein measuring the Anterior Chamber Depth of the pre-operative eye of the patient comprises performing an optical technique selected from the group consisting of: visible depth measurement; interferometry; partial interferometry; low coherence interferometry; Scheimpflug imaging; laser interferometry; and laser biometry. 
     
     
       18. The method according to  claim 1  wherein measuring the thickness of the crystalline lens in the pre-operative eye of the patient in step (ii) comprises performing an ultrasound technique. 
     
     
       19. The method according to  claim 1  wherein measuring the thickness of the crystalline lens in the pre-operative eye of the patient in step (ii) comprises performing laser interferometry or laser biometry. 
     
     
       20. The method according to  claim 1  wherein calculating the post-operative position of the intraocular lens in step (iii) comprises executing the formula:
   IOL predicted =ACD pre   +C×LT    
 
       wherein:
 IOL predicted  is the predicted post-operative position of the intraocular lens in the eye of the patient; 
 ACD pre  is the pre-operative Anterior Chamber Depth of the eye of the patient; 
 C is a numerical constant, as discussed above; and 
 LT is the thickness of the crystalline lens in the pre-operative eye of the patient. 
 
     
     
       21. The method according to  claim 1  wherein step (b) comprises establishing an optical model of the post-operative eye of the patient. 
     
     
       22. The method according to  claim 21  wherein establishing an optical model of the post-operative eye of the patient comprises measuring one or more property of the pre-operative eye of the eye of the patient, selected from the group consisting of: the optics of the cornea; the corneal radius; the length of the eye; the axial length; the anterior chamber depth; and the crystalline lens thickness. 
     
     
       23. The method according to  claim 21  wherein step (b) further comprises analysing the optical properties of the optical model of the post-operative eye of the patient. 
     
     
       24. The method according to  claim 23  wherein analysing the optical properties of the optical model of the post-operative eye of the patient comprises performing an exact ray tracing analysis. 
     
     
       25. The method according to  claim 23  wherein analysing the optical properties of the optical model of the post-operative eye of the patient comprises performing a paraxial ray tracing analysis. 
     
     
       26. The method according to  claim 1  further comprising the step of
 designing an intraocular lens having a power and geometry required to provide the desired optical property in the post-operative eye of the patient prior to step (c). 
 
     
     
       27. The method according to  claim 26  wherein step (b) comprises establishing an optical model of the post-operative eye of the patient. 
     
     
       28. The method according to  claim 27  wherein establishing an optical model of the post-operative eye of the patient comprises measuring one or more property of the pre-operative eye of the eye of the patient, selected from the group consisting of: the optics of the cornea; the corneal radius; the length of the eye; the axial length; the anterior chamber depth; and the crystalline lens thickness. 
     
     
       29. The method according to  claim 27  wherein step (b) further comprises analysing the optical properties of the optical model of the post-operative eye of the patient. 
     
     
       30. The method according to  claim 29  wherein analysing the optical properties of the optical model of the post-operative eye of the patient comprises performing an exact ray tracing analysis. 
     
     
       31. The method according to  claim 30  wherein analysing the optical properties of the optical model of the post-operative eye of the patient comprises performing a paraxial ray tracing analysis.